Towers pose a special danger to some 350 species of night-migrating songbirds, especially on foggy or cloudy nights.
Researchers have observed bird kills at communications towers for decades, with one estimate in the 1970s placing the number of birds killed at 1.4 million birds per year. That estimate was based on the 1,100 tall towers then in existence.
Today there are more than 75,000 towers taller than 200 feet nationally. Predictions are there will be more than 100,000 towers added to the landscape in the next decade.
The Federal Aviation Administration tracks the number of towers across the continent to monitor aviation hazards. From the mid-1970s through the early 1990s, new tower construction (200 feet tall or higher) had been proceeding at about the rate of about 1,000 per year. But in the 1990s, due to the birth of the cell phone and personal service (pcs) industry, the FAA estimates new tower construction in the U.S. had accelerated to over 5,000 per year.
Because of Federal Communication Commission mandates to digitize all television stations by the year 2003, at least 1,000 of these new towers will exceed 0.2 miles in height, creating a potentially serious threat to birds.
This problem is certainly hitting close to home. In Minnesota, as of November 1998, there were 1,014 towers spread out across the state. In viewing an Internet graphic of Minnesota, I was surprised to see not one area devoid of towers -- not even the pristine Boundary Waters Canoe area. The breakdown of tower heights and numbers is:
-- 200-299 feet -- 382 towers
-- 300-499 feet -- 540 towers
-- 500-799 feet -- 67 towers
-- 800+ feet -- 25 towers
There are not long-term studies at communications towers below 500-feet high. However, it is widely agreed the taller a communication tower, the more deadly it is for night-migrating songbirds. In addition, much seems to rely on the tower's location. Evidence suggests a relatively short tower constructed on a hilltop may have the same impact as higher towers on flat ground.
Long-term studies of bird mortality at tall communications towers all indicate that sizable kills occur on a regular basis, with occurrences depending on specific weather conditions. Consequently, all show a considerable range of numbers killed from year to year -- thousands may be killed in one season while only a few dozen the next.
Below is a list of locations of some of North America's long-term studies with the tower height, study period, number of birds killed and an indication of how regularly the tower was checked.
-- 1000-ft. tower in Eau Claire, Wis., 1957-1994
121,560 birds killed/123 species/checked daily in the migration seasons
-- 1368-ft. tower in Nashville, Tenn., 1960-1997
19,880 birds killed/112 species/checked daily in the migration seasons
-- 850-ft. tower in Elmira, N.Y., 1963-1983
over 7500 birds killed/checked daily in fall migration season
-- 529-ft. tower near Weston, W.Va., 1978-1986
841 birds killed/58 species/checked irregularly in the migration seasons
Hundreds of short-term studies have been conducted consisting of data gathered from just a single night or over several years. Due to weather variables these studies are less reliable for gauging continental mortality, though they do confirm that kills regularly occur over a wide area of North America.
Recognition of the disturbing phenomenon led the Ornithological Council to issue a Towerkill Resolution in April 1998. The group's concern was heightened by their belief the accrued impact of thousands of towers on migrant songbird populations may be significant for declining species such as Cerulean Warblers and endangered species such as Kirtland's Warbler.
The resolution urged the FAA to endorse studies involving experiments toward finding lighting systems for towers that reduce avian mortality. It also encouraged the communications industry to voluntarily reduce the number of new towers by co-locating new transmitters on existing towers and to work with the U.S. Fish & Wildlife Service (USFWS) to minimize collisions.
It further strongly prevailed upon the USFWS to work with the FAA and the Federal Communications Commission to study the magnitude of the problem, including thorough preparation of an Environmental Impact Statement, and to develop a national plan to address the problem.
In August 1999 the USFWS co-hosted a groundbreaking workshop at Cornell University in Ithaca, New York, to examine the dilemma. The workshop brought together leading ornithologists, federal and state agencies as well as industry and conservation organizations from across the country to discuss the situation and begin deciding a course of action.
Co-sponsored by the American Bird Conservancy and the Ornithological Council, the workshop was held in conjunction with the 117th meeting of the American Ornithologists' Union.
The USFWS has long worked with the electric utility and wind generation industries to help solve bird collision and electrocution problems, and would like to forge a similar partnership with the communications industry.
Albert Manville, USFWS wildlife biologist and co-chair of the Cornell Workshop on Avian Mortality at Communication Towers, stated "Regarding the big picture, we are most concerned about the cumulative impacts of all towers on birds, combined with all the other things that kill them -- habitat degradation and loss, pesticides, glass windows, domestic cats, power lines, wind generators, cars, aircraft, oil spills, and such."
There are things the communications industry can do now to minimize impacts on birds. "Communications companies can reduce deaths by co-locating communications equipment on existing towers and buildings. If a new tower is necessary, it can be build without guy wires and, where possible, left unlighted or with lights that are less attractive to birds," Manville said.
Clearly this problem is not going to go away. As we survey the changing landscape of our nation, state and local lake country, we must step up to the challenge of solving a situation for which we are responsible. It's going to mean personally giving up or limiting some conveniences, assessing tower impact on wildlife and aesthetic and working with the communications industry to implement techniques to curb bird collisions with communication towers.
(Sources: USFWS, Towerkill.com, et al)
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